IBOC, Subcarriers and Channel 6

In the previous two issues, Radio World has excerpted comments that were submitted to the FCC about the National Radio Systems Committee report on Ibiquity Digital Corp.'s FM in-band, on-channel digital audio broadcasting system.

In the previous two issues, Radio World has excerpted comments that were submitted to the FCC about the National Radio Systems Committee report on Ibiquity Digital Corp.'s FM in-band, on-channel digital audio broadcasting system.

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In the previous two issues, Radio World has excerpted comments that were submitted to the FCC about the National Radio Systems Committee report on Ibiquity Digital Corp.'s FM in-band, on-channel digital audio broadcasting system.

Station groups, commercial and noncommercial, made up the bulk of the filings, along with transmission and receiver manufacturers, trade associations and public interest groups. Most of the remarks were positive; some criticisms were lodged. This is a sampling ...

"The commission should also include the use of new spectrum from the 82-88 MHz band (TV Channel 6) to enable prompt realization of the full benefits of DAB without interfering with existing analog stations. ...

"The only potential drawback to the use of Channel 6 is the fact that this spectrum might not be available in all markets in 2007 if transition to digital television is delayed. The potential drawbacks to reliance solely on IBOC are possible lower quality of service, reduced coverage and deferral of some of the benefits of DAB until after the analog systems are removed from the band. ...

"As the FCC has recognized, IBOC systems can cause adjacent-channel interference to analog stations during the transition and result in loss of actual coverage for existing stations. Modern receivers dynamically change their internal operating parameters (mono/stereo blending, diversity antenna switching) based on high-frequency noise measurements of the recovered baseband signal. With the addition of an increased power density between 100-200 kHz from an IBOC FM DAB signal, there exists the real potential that this additional signal will cause undesired, and still unknown, performance changes to existing analog receivers. ...

"Both IBOC and TV Channel 6 options will cost more than the present analog service, but not as much as the cost of a completely new frequency band. A single tuner can bridge both TV Channel 6 and the adjacent FM broadcast band. ...

"We can learn from the experience of Europe and Canada in implementation of the Eureka 147 DAB system. This system has yet to enjoy widespread market acceptance because of the increased cost of the receivers is not balanced against programming or service gains. ... Eureka 147 receivers cost several hundred dollars more than conventional receivers because of the need to accommodate an additional tuner for the L-band or VHF Band III, the additional digital decoding circuitry, and a different antenna. ...

"Both the Channel 6 and IBOC solutions will cost less than Eureka 147. Both IBOC and Channel 6 will require the same fundamental building blocks for decoding the digital signals, such as analog/digital converters, digital demodulators, de-interleaving circuitry, audio decoders, clock circuitry, and control circuitry.

"Both would use the current FM antennas and neither would need a separate tuner, although both would require some modifications to the current analog tuners. Both Channel 6 and IBOC should thus cost less than Eureka 147, but more than current AM/FM analog radios. If TV Channel 6 is added to the DAB/FM band, some small additional cost over the IBOC receiver may be needed in order to expand the range of the tuner to cover the entire band 82-108 MHz."

-- Visteon Automotive Systems

"Today there are many subsidiary services on subcarriers which occupy the FM broadcast band - a band which was awarded for free as a public trust. Some, including reading services for the blind, are important and worthy. Other subsidiary services are strictly for-profit enterprises, such as data carriers and pager services. Until now, the commission has not actively regulated the use of these frequencies, so long as they have met certain reasonable technical parameters. ...

"We ... understand and appreciate the restraint that the commission has shown in the past regarding subcarrier content. We believe, however, that this policy has outlived its usefulness.

"In the near future, subcarriers may become nearly as important economically as the main carrier of the radio station. With the implementation of more sophisticated radio services, the utilization of the lucrative SCAs may hold the keys to the future business models of radio, perhaps creating interactive opportunities for listeners or other new features for radio.

"In all likelihood, many of these implementations will be crass revenue generators, including services that permit a listener to directly purchase a recording that is being broadcast. IBOC is, in fact, the demon spawn of the vague subcarrier policy."

-- Pete Tridish, staffer Prometheus Radio Project

"The commission has ... begun to seek comment on 'whether the 6 Megahertz at 82-88 MHz, currently used for TV Channel 6, could be reallocated to DAB service at the end of the DTV transition...(and) whether this spectrum could be reallocated without adversely affecting the broadcast television service.'

"The short answer is 'no.' In light of the commission's prior findings and the reliance of Freedom and other television broadcasters on the rulings of the commission that Channel 6 will be available for DTV, any use of the 82-88 MHz band for DAB would adversely affect the broadcast television service.

"If the commission were to reallocate Channel 6 for DAB, the DTV strategy of Freedom and other Channel 6 licensees will be significantly disrupted and Channel 6 television licensees would bear a disproportionate share of the cost of DTV implementation."

In the Sept. 1 issue, Radio World published a selection of comments filed with the FCC about the NRSC report on Ibiquity Digital Corp.'s AM in-band, on-channel digital audio broadcasting system. Here is another sampling...

WASHINGTON The FCC wants public comments on a report from the National Radio Systems Committee. The NRSC ecommends that Ibiquity Digital Corp.’s FM system be adopted as the in-band, on-channel digital radio system for FM in the United States.

If the hopes and expectations of iBiquity Digital Corp. come to pass, engineers will be scrambling this time next year to prepare their facilities for the in-band, on-channel digital broadcasting revolution.

For years, Ibiquity Digital Corp. and its former incarnation USA Digital Radio have pursued several paths in the hope of making in-band, on-channel the terrestrial radio digital technology for the United States.

This is one in a series in which Ibiquity Digital Corp. answers questions about how to implement in-band, on-channel digital audio broadcasting. Broadcast Technology Manager Jeff Detweiler answers here.

This is the second in a series of articles in which representatives of Ibiquity Digital Corp. answer common questions about the implementation of in-band, on-channel digital audio broadcasting. Broadcast Technology Manager Jeff Detweiler answers today’s query.